The present invention relates to a liquid device, liquid device manufacturing apparatus and method, and an image display device, and particularly to a liquid device, liquid device manufacturing apparatus and method, and an image display device that are so configured as to achieve increase in the dielectric constant and be capable of suppressing the occurrence of breakdown.
Conventionally, there is an electrowetting technique in which deformation and displacement of a liquid are generated by utilizing electrowetting of controlling the electrostatic wettability and the desired effect is achieved by this phenomenon, and utilizing this technique in various fields is considered.
For example, for an optical shutter employing a liquid crystal, various improvement methods are carried out, such as improvement in the angle between the liquid crystal molecules and the polarizer absorption axis (refer to e.g. Patent document 1), improvement in electric field application (refer to e.g. Patent document 2 and Patent document 3), alignment treatment (refer to e.g. Patent document 4), and provision of recesses and projections on a substrate (refer to e.g. Patent document 5). However, all of the cases involve problems such as low light extraction efficiency and very-low response speed, and a method of using the above-described electrowetting technique instead of these methods is considered.
Furthermore, for example, as methods for increasing the number of parallaxes in a three-dimensional display device, there is a method in which a micro-lens array is moved relative to a light-emitting pixel and light is refracted to plural directions (refer to e.g. Patent document 6) and a method in which the position of the droplet of a liquid lens is controlled (refer to e.g. Patent document 7). However, a method of using the electrowetting technique instead of these methods is considered.
Moreover, utilizing this electrowetting technique also for a focus variable lens whose focal length is arbitrarily varied, flow path control of a liquid, a liquid pump, and so on is considered.
The principle of such an electrowetting technique will be described.
FIG. 1 is a diagram showing a basic configuration example of a liquid device to which the electrowetting technique is applied.
As shown in FIG. 1, in a liquid device 1, an insulating water-repellent film 12 having water repellency against a polar liquid 13 is formed on one electrode 11, and the other electrode 14 is provided for the polar liquid 13 disposed on the water-repellent film 12. The voltage of a power supply 15 is applied between the electrode 11 and the electrode 14. The wettability of the polar liquid 13 to the water-repellent film 12 changes depending on the magnitude of this applied voltage, and the contact angle θ between the polar liquid 13 and the water-repellent film 12 changes. That is, the interfacial shape of the polar liquid 13 changes. Therefore, for example, the liquid device 1 can exert influences on the optical path of transmission light that passes through this polar liquid by controlling the magnitude of the applied voltage.
More specifically, the following equations (1) to (3) apply to the wettability of the polar liquid 13 to the water-repellent film 12.γLV cos θ=γSVγSL+γEW  (1)γEW=d×σL2/2×ε0×εr  (2)σL=ε0×εr×V/d  (3)
In these equations, γLV denotes the interfacial tension between the liquid and the vapor. γSV denotes the interfacial tension between the solid and the vapor. γSL denotes the interfacial tension between the solid and the liquid. γEW denotes the interfacial tension dependent on the intensity of the electric field. ε0 denotes the permeability of vacuum. εr denotes the relative dielectric constant of the water-repellent film 12. Furthermore, V denotes the magnitude of the applied voltage, and d denotes the length between the electrodes.
That is, the wettability of the polar liquid 13 to the water-repellent film 12 changes depending on the magnitude of the applied voltage, and the polar liquid 13 deforms or moves.
In addition to this, there is also e.g. a method in which the polar liquid 13 is moved or deformed by changing the voltage application position. The principle of this method is similar to that of the above-described case. Moreover, there is also another method. In this method, in addition to the polar liquid 13, a nonpolar liquid that does not mix with the polar liquid 13 and is not affected by the applied voltage is provided. This nonpolar liquid is pushed by the polar liquid 13 whose shape is changed by the applied voltage, so that the shape of the nonpolar liquid changes. The desired effect is achieved by this shape change of the nonpolar liquid. The principle of this method is similar to that of the case of FIG. 1.    Patent document 1: Japanese Patent Laid-open No. 2005-284261    Patent document 2: Japanese Patent Laid-open No. 2003-262847    Patent document 3: Japanese Patent Laid-open No. 2002-131717    Patent document 4: Japanese Patent Laid-open No. 2002-148625    Patent document 5: Japanese Patent Laid-open No. 2000-347171    Patent document 6: Japanese Patent Laid-open No. 2002-176660    Patent document 7: Japanese Patent Laid-open No. 2003-215478